Backport #2062 to 3-0-stable (#2176)

* Do not allow BodyProxy to respond to to_str, make to_ary call close

See rack/rack-test#335 for an example
where allowing BodyProxy to respond to to_str (when provided an
invalid rack body) complicated debugging.

Call BodyProxy#close if BodyProxy#to_ary is called, as not doing so
violates SPEC.

* Changelog for #2062

---------

Co-authored-by: Jeremy Evans <code@jeremyevans.net>

CHANGELOG.md

@@ -4,6 +4,8 @@ All notable changes to this project will be documented in this file. For info on
 
 ## Unreleased
 
+- Backport #2062 to 3-0-stable: Do not allow `BodyProxy` to respond to `to_str`, make `to_ary` call close . ([#2062](https://github.com/rack/rack/pull/2062), [@jeremyevans](https://github.com/jeremyevans))
+
 ## [3.0.10] - 2024-03-21
 
 - Backport #2104 to 3-0-stable: Return empty when parsing a multi-part POST with only one end delimiter. ([#2164](https://github.com/rack/rack/pull/2164), [@JoeDupuis](https://github.com/JoeDupuis))

lib/rack/body_proxy.rb

@@ -15,7 +15,12 @@ def initialize(body, &block)
 
     # Return whether the wrapped body responds to the method.
     def respond_to_missing?(method_name, include_all = false)
-      super or @body.respond_to?(method_name, include_all)
+      case method_name
+      when :to_str
+        false
+      else
+        super or @body.respond_to?(method_name, include_all)
+      end
     end
 
     # If not already closed, close the wrapped body and
@@ -38,7 +43,18 @@ def closed?
 
     # Delegate missing methods to the wrapped body.
     def method_missing(method_name, *args, &block)
-      @body.__send__(method_name, *args, &block)
+      case method_name
+      when :to_str
+        super
+      when :to_ary
+        begin
+          @body.__send__(method_name, *args, &block)
+        ensure
+          close
+        end
+      else
+        @body.__send__(method_name, *args, &block)
+      end
     end
     # :nocov:
     ruby2_keywords(:method_missing) if respond_to?(:ruby2_keywords, true)

test/spec_body_proxy.rb

@@ -74,13 +74,37 @@ def body.banana(foo: nil); foo end
     proxy.banana(foo: 1).must_equal 1
   end
 
-  it 'not respond to :to_ary' do
-    body = Object.new.tap { |o| def o.to_ary() end }
-    body.respond_to?(:to_ary).must_equal true
+  it 'respond to :to_ary if body does responds to it, and have to_ary call close' do
+    proxy_closed = false
+    proxy = Rack::BodyProxy.new([]) { proxy_closed = true }
+    proxy.respond_to?(:to_ary).must_equal true
+    proxy_closed.must_equal false
+    proxy.to_ary.must_equal []
+    proxy_closed.must_equal true
+  end
 
-    proxy = Rack::BodyProxy.new(body) { }
-    x = [proxy]
-    assert_equal x, x.flatten
+  it 'not respond to :to_ary if body does not respond to it' do
+    proxy = Rack::BodyProxy.new([].map) { }
+    proxy.respond_to?(:to_ary).must_equal false
+    proc do
+      proxy.to_ary
+    end.must_raise NoMethodError
+  end
+
+  it 'not respond to :to_str' do
+    proxy = Rack::BodyProxy.new("string body") { }
+    proxy.respond_to?(:to_str).must_equal false
+    proc do
+      proxy.to_str
+    end.must_raise NoMethodError
+  end
+
+  it 'not respond to :to_path if body does not respond to it' do
+    proxy = Rack::BodyProxy.new("string body") { }
+    proxy.respond_to?(:to_path).must_equal false
+    proc do
+      proxy.to_path
+    end.must_raise NoMethodError
   end
 
   it 'not close more than one time' do